Organic Pest and Disease Control

From the Community Gardening in SA Resource Kit. Originally written by David Corkill for organic
gardening courses at Fern Ave Community Garden. May be reproduced for use in community

The aim of organic pest control
is to reduce damage to an
acceptable minimum. It is
neither possible nor desirable to
eliminate all pests completely
from the garden.
Natural balance
If the right conditions are
created in the garden, a host of
useful predators and parasites
can be encouraged to move into
the garden and do the pest
control for you. These conditions
are habitat (somewhere to live)
and food (pests or other food
used during different times of
the predators’ life-cycle). The
best way to maintain the
conditions required for a range
of useful organisms in the
garden is to grow a diversity of
plants and to avoid the
temptation to try to eliminate all
pests.
Some commonly found useful
garden predators and parasites
are birds, lizards, frogs, spiders,
ladybirds, hover flies, lacewings,
dragon flies, praying mantis,
centipedes, parasitic wasps, and
predator mites. Small children
with instructions to collect snails
can be useful too.
Soil Conditions
Improving soil quality can reduce the occurrence and impact of pest
and disease in the garden. Plants grown in good healthy soil will be
healthy and healthy plants are disease resistant. Fungi and moulds in
healthy soil produce natural antibiotics, cleansing the soil and aiding
plants’ disease resistance. Unhealthy plants, including plants raised on
artificial fertilisers, attract pests. Healthy plants will resist pest
attack and outgrow pest damage.
Organic sprays and dusts
Materials with natural insecticidal properties, which quickly break
down and do not cause contamination may be used to kill garden
pests. They will also kill many useful organisms so only use as a last
resort.
Pyrethrum - The dried flower heads of the pyrethrum daisy are used
to make an insecticide spray, Though non-residual, the spray is quite
strong and should be used with caution.
Neem - Oil extracted from the Neem tree has insecticidal, fungicidal
and antiseptic properties.
Quassia - The wood and bark of the Quassia tree, from South
America, is a mild insecticide. Quassia chips can be kept in long term
storage with little loss of potency.
Bacillus thuringeinsis - A micro-organism that acts as a stomach
poison for caterpillars. Sold under the name “Dipel”.
Sulphur - A yellow mineral used as a powder. Fungicide and miticide.
May damage tender plants.
White oil - Mineral oil used to control scale. Acceptable for occasional
use.
Repellent sprays
Home-made repellent sprays are prepared as per herb tea then
sprayed to protect vulnerable plants. Some have mild insecticidal
properties. They include garlic, rhubarb, cloves, aniseed, sage,
camphor, chillies, chives, onion, feverfew, wormwood, tansy. Mixing
soap with a spray improves its wetting ability and increases the
insecticidal effect.